Frequency-Dependent Dielectric Properties of Polymer-Based BT Nanocomposites with High Energy Density

摘要

Nanodielectric materials become one of the key materials to play an important role in sustainable and clean energy production, energy transformation, energy storage, and end usage in terms of energy storage capabilities due to the trade-off between dielectric constant, dielectric loss and voltage breakdown. Based on our recent research on BaTiO_3 (BT) nanoparticles, BT/Parylene and BT/P(VDF-HFP) nanocomposites, frequency dependent dielectric properties of such material systems with high energy density have been investigated as a function of the volume fraction of nanoparticles at room temperature by several theoretical models. For single domain and single crystals of BT a Debye type of dissipation and soft mode theory has been developed to obtain more precise frequency dependent dielectric spectrum of BT. For nanodielectric composites, among the others, Lichtnecker model, Maxwell-Wagner model, Yamada, and modified Kerner model were adopted to evaluate frequency dependent dielectric spectrum of nanocomposites. A simple rule of mixture for the dielectric loss tangent was obtained using Lichtnecker logarithmic rule. The results from theoretical calculations are compared with the experimental data. For dielectric constant, Lichtnecker model, Maxwell-Wagner model and Yamada model show reasonable agreements with the experimental data up to 50% volume fraction of the nanoparticles. For dielectric loss, the simple rule of mixture gives good predictions for a wide frequency range and showed reasonable agreements with experimental data. This theoretical study provides an essential information on dielectric properties of polymer-based BT nanocomposites with a wide frequency range instead of trial-and-error strategy of experiments and can be used for designing high energy density dielectric materials in the future.